Does Access to Medical Cannabis Reduce Risk for Opioid Abuse?

Contrasting evidence found in state-level and person-level analyses should serve as a caution to eager advocates and puzzled policymakers.

According to data from the Centers for Disease Control and Prevention, deaths from drug overdose have continued to increase in the United States in recent years, with more 600,000 reported from 2000 to 2016.1 Prescription opioids have been identified as a key factor driving this surge; approximately 63% of the 52,404 overdose deaths in 2015 involved an opioid.2

Various strategies have been introduced to address this crisis, including implementation of the CDC Guideline for Prescribing Opioids for Chronic Pain, as well as efforts to improve prescription drug monitoring programs and access to treatment for opioid use disorder. In the ongoing search for solutions, it has been suggested that access to medical cannabis may lead to a reduction in opioid use for pain management.3

In an analysis published in 2014, a 21% reduction in mean annual opioid overdose mortality was found in states with legalized medical cannabis.4 Other findings show that the use of prescriptions for numerous conditions decreased following the legalization of medical cannabis, but the greatest reduction was observed for medications indicated for pain treatment.5

Although these results may seem to support a link between increased access to cannabis and a reduction in prescription opioid use, findings from a study published in 2018 found otherwise (although this investigation focused on cannabis generally rather than legalized medical cannabis).6 Researchers at Columbia University Medical Center and the National Institute on Drug Abuse used logistic regression models to analyze data from wave 1 (2001-2002) and wave 2 (2004-2005) of the National Epidemiologic Survey on Alcohol and Related Conditions.

Their analysis of more than 34,000 US adults revealed associations between cannabis use at wave 1 and increased use of nonmedical prescription opioids (odds ratio [OR], 5.78; 95% CI, 4.23-7.90) and opioid use disorder (OR, 7.76, 95% CI, 4.95-12.16) at wave 2, which remained significant after controlling for background characteristics of participants, including age, sex, anxiety or mood disorders, and family history of substance abuse.

Although these results do “not resolve the debate about associations between medical cannabis use, use of prescription opioids, and risks of opioid overdose mortality…. (t)he study is nonetheless an important contribution that balances the state-level analyses with individual level data,” wrote Dennis McCarty, PhD, a professor of public health and preventive medicine at Oregon Health & Science University, in an editorial about the study that appeared in the same issue of the American Journal of Psychiatry.3 He pointed to the large dataset and consistency of participants across waves as strengths of the study, and he cited the dated and self-reported nature of the data, as well as the lack of differentiation between medical and nonmedical cannabis use, as limitations.

“The contrasting associations from the state-level and the person-level analyses should serve as a caution to eager advocates and puzzled policymakers. It is too soon for science to provide deﬁnitive guidance,” added Dr McCarty.

“It is time, therefore, in states where cannabis use is authorized for adults, to build patient registries of cannabis use that link with medical records so that it is feasible to assess morbidity and mortality associated with the frequency, duration, and method [of use],” he wrote.

To further explore the implications of the new findings, Psychiatry Advisor interviewed Mark Olfson, MD, professor of psychiatry at Columbia University Medical Center, who is one of the authors of the study.6

Psychiatry Advisor:What are the top takeaways from your study?

Dr Olfson: As compared with adults who did not smoke marijuana, those who smoked marijuana were found 3 years later to be almost 6 times more likely to misuse prescription opioids and almost 8 times more likely to have an opioid use disorder. Even though [opioid problems did not develop in] most people who smoked marijuana at the start of the study, those who did were at a significantly higher risk [for these problems] developing than were those who did not smoke marijuana. Contrary to some previous reports that were based on population-level patterns, we found that marijuana use tends to increase rather than decrease the risk for prescription opioid use abuse or dependence.

Psychiatry Advisor:What are the overall treatment implications for mental health and pain clinicians?

Dr Olfson: We found that cannabis use, even among adults with moderate or severe pain, was associated with a substantially increased risk for problematic prescription opioid use 3 years later. Although this study was not designed to directly address questions over the appropriate role of medical marijuana in the management of chronic medical pain conditions, the results nevertheless suggest that pain specialists should consider vulnerabilities to addiction when deciding whether to recommend medical marijuana for their patients with persistent pain.

Psychiatry Advisor:What should be the focus of future research in this area?

Dr Olfson: We're currently working on trying to understand precursors to fatal opioid overdoses. We're focusing on trying to identify characteristics of patients with non-fatal opioid overdoses who are at the highest short-term risk for overdose death so that more can be done to interrupt this dangerous course by making active efforts to engage them in medication-assisted treatment.